The present invention relates to a wound dressing comprising at least one layer of microbially produced cellulose (biocellulose layer). The wound dressing is designed such that it adsorbs bacteria. The invention further relates to a method for producing such a wound dressing.
Wound dressings for healing burns, skin lesions or poorly healing wounds are known. Thus U.S. Pat. No. 4,588,400 A, U.S. Pat. No. 4,655,758 A and U.S. Pat. No. 4,788,146 A describe materials for such applications, which are produced on the basis of microbially produced cellulose. These documents also describe that the biocellulose layer can be impregnated with bacteriostatic agents such as silver nitrate or benzalkonium chloride. Methods for producing biocellulose are also described in WO 86/02095 A1 and WO 2004/050986 A. EP 1 356 831 A also describes the application of biocellulose in the treatment of wounds.
According to WO 2005/009276 A biocellulose can be provided with polyhexamethylene biguanide hydrochloride to impart antimicrobial activity. The corresponding wound dressings are intended to release moisture and are accordingly characterized by a very high water content and a correspondingly low cellulose content. In WO 2005/009276 A wound dressings are used specifically for chronic wounds. However, for burns, excessive moisture can be contraindicated.
EP 1 438 975 A discloses a moisture-releasing amorphous hydrogel based on microbial-derived cellulose for application to wounds.
In addition to the mentioned disadvantages of a high moisture (contraindicated for burns) the infection of the wound can be increased by such a gel.
The product Cuticell® Epigraft from BSN medical GmbH, Hamburg, Federal Republic of Germany, consists of a pure cellulose membrane which is formed by the microorganism Acetobacter xylinum. The product is transparent and thus allows the healing of the wound to be observed during treatment without the wound dressing having to be destroyed. Such biocellulose-based wound dressings are suitable for the treatment of split-skin graft donor sites, burns, skin cracks, wounds and skin lesions (such as skin abrasions, incised wounds and small surgical wounds). However, commercially available biocellulose-based wound dressings are thin and thus delicate during application. If applied incorrectly, contamination can easily occur. Thus infected wounds cannot be treated with biocellulose-based wound dressings. There is thus a requirement for wound dressings which can also be used for infected wounds as well as chronic wounds with exudate.
Bacteria-adsorbing compositions are also known. Thus EP 0 162 026 A describes that bacteria-adsorbing compositions can be used for treating external infections, which leads to a better removal of bacteria and other microorganisms. The compositions contain a hydrophilic material such as cotton which is rendered hydrophobic by treatment with for example dialkyl carbamoyl chloride.
Moreover WO 2006/062470 A discloses a wound dressing which has, on the side facing the wound, a hydrophobic layer which binds such microorganisms, above it an absorbent, hydrophilic layer, and a preferably transparent polyurethane layer as cover layer. The main task of such products is to adsorb bacteria, i.e. the field of use of such products is limited and they must always be combined with a further wound dressing. Such products are thus suitable particularly for short-term wound coverage.
DE 196 31 421 A also deals with hydrophobized carrier materials which can adsorb bacteria. The product Cutisorb® Sorbact® from BSN medical GmbH, Hamburg, Federal Republic of Germany, has for example a layer of hydrophobized acetate or cotton fabric.
DE 101 35 676 A discloses that (optionally microbially produced) cellulose can be doped with chitosan, hyaluronic acid or derivatives or mixtures thereof. The doped film is used, among other things, as physiological diaphragm, artificial bloodstream and/or a pump for infusion or dialysis. In such applications it is impossible for proteins to be absorbed, which is why the films according to DE 101 35 676 A do not adsorb bacteria.